In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient through a vessel and advanced therein until the distal end of the catheter is at a desired location in the vasculature. A guidewire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guidewire sliding through the dilatation catheter. The guidewire is first advanced out of the guiding catheter into the patient""s coronary vasculature and the dilatation catheter is advanced over the previously advanced guidewire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a liquid or gas at relatively high pressures, such as greater than about four atmospheres, to radially compress the arthrosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.
In angioplasty procedures of the kind described above, there may be restenosis of the artery, which either necessitates another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To help prevent restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency inside the artery at the lesion. The intravascular prosthesis or stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Examples of balloon expandable stents are provided in U.S. Pat. No. 5,807,404 and U.S. Pat. No. 5,868,781. The stent is delivered on a stent delivery catheter. Examples of stent delivery catheters include those disclosed in U.S. Pat. No. 5,944,726, U.S. Pat. No. 5,772,669 and U.S. Pat. No. 4,733,665.
During the delivery of a balloon expandable stent to a desired bodily location, the stent may move relative to the balloon resulting in a non-uniform expansion of the stent and rendering difficult the accurate deployment of the stent. It is, therefore, desirable, in delivering a balloon expandable stent to a desired bodily location, to secure the stent to the balloon prior to expansion of the balloon and stent. A number of stent securement methods and devices have been proposed. U.S. Pat. No. 5,944,726 discloses several stent securement devices including mounting bodies. U.S. Pat. No. 4,950,227 discloses the use of sleeves disposed over a portion of the proximal and distal ends of a stent.
For the purpose of this disclosure, all U.S. patents and patent applications and all other publications referenced herein are incorporated herein by reference in their entirety.
Without limiting the scope of the invention in any way, the invention is briefly summarized below.
The present invention is directed in one embodiment to a method of forming a medical balloon structure. In accordance with the inventive method, a tube is provided and an inner structure selected from the group consisting of medical balloons and medical balloon tubes is also provided. The tube is disposed about the inner structure. The tube and inner structure are then placed in a balloon mold and a predetermined pressure, tension and temperature are applied to the tube and inner structure so as to form a medical balloon structure. The thus formed medical balloon structure includes a proximal cone portion, a body portion and a distal portion and has an outer wall formed from the tube and an inner wall formed from the inner structure. At least a portion of the outer wall is removed from the body portion of the medical balloon structure. Desirably, the entirety of the outer wall in the region of the body portion is removed.
The invention is also directed to a method of forming medical balloon structures comprising the steps of providing an inner structure selected from the group consisting of medical balloons and medical balloon tubes and a plurality of tubes disposed in layers about the inner structure and placing the inner structure and tubes in a mold. The inner structure and plurality of tubes are then molded at a predetermined pressure, tension and temperature so as to form a medical balloon structure having proximal and distal cone portions and a body portion. Subsequent to molding, a desired number of layers of tube are removed from the body portion of the medical balloon structure.
The invention is also directed to medical balloons formed in accordance with the inventive methods. In particular, the invention is directed to a medical balloon structure having been formed of an inner structure selected from the group consisting of medical balloons and medical balloon tubes and a tube disposed thereabout. The inner structure and tube are molded to form a medical balloon structure having proximal and distal cone portions and a body portion. At this stage, the tube forms the outer wall of the medical balloon structure and the inner structure forms the inner wall of the medical balloon structure. A portion of the outer wall, desirably, the entirety of the outer wall, is then removed from the body portion of the medical balloon structure to form the inventive medical balloon structure.
The invention is also directed to medical balloon structures formed from an inner structure selected from the group consisting of medical balloons and medical balloon tubes and a plurality of tubes disposed in layers about the inner structure. The inner structure and plurality of tubes are molded so as to form a medical balloon structure having proximal and distal cone portions and a body portion. Subsequent to molding, a desired number of layers of tube are removed from the body portion of the medical balloon structure.
In yet another embodiment, the invention is directed to a medical balloon structure comprising a proximal cone portion, a distal cone portion and a body portion. The proximal cone portion, distal cone portion and body portion each have a number of layers of material. At least a portion of the body portion has fewer layers of material than at least one of the proximal and distal cones.
The invention is further directed to catheters comprising the inventive medical balloons. One such catheter is a stent delivery catheter employing an inventive balloon. Desirably, at least one outer layer of the proximal and distal cone sections will be moved toward one another and reside over portions of the proximal and distal ends of the stent.
In another aspect, the invention is directed to a method for fastening a stent to a catheter in a manner suitable for introduction, and later release, of the stent to a body cavity. The method includes the steps of (a) providing a catheter having an inventive medical balloon structure as disclosed above disposed about a distal portion thereof; (b) providing a stent having a contracted and an expanded condition; (c) disposing the stent about the body portion of the medical balloon structure; and (d) pulling a portion of the proximal and distal cones toward one another so that a portion of the proximal cone is disposed over a proximal portion of the stent and a portion of the distal cone is disposed over of a distal portion of the stent thereby fixing the stent to the catheter when the stent and medical balloon structure are in their contracted state or condition.
In yet another aspect of the invention, the invention features a method for positioning a stent within a body cavity, including the steps of (a) providing a stent delivery system with an inventive medical balloon structure and stent secured thereto; (b) introducing the stent delivery system into the body cavity; (c) causing the medical balloon structure to expand and thereby simultaneously expanding the stent and causing the portions of the cone section which overlie the proximal and distal portions of the stent to be released from their position overlying the stent, at least partially contracting the catheter, and (d) removing the catheter from the body cavity by axially pulling the catheter from the body cavity.